diffusefraction.py

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# This scripts calculates the diffuse and directbeam radiation according to Reindl et al (1990)                                              #
# source : https://github.com/UMEP-dev/UMEP/blob/6fc4a1adaf5b66096b4d3dd558b867d44a04496c/Utilities/SEBESOLWEIGCommonFiles/diffusefraction.py#  
# Goteborg Urban Climate Group                                                                                                               #
# Gothenburg University                                                                                                                      #
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import numpy as np
from sunpos import altitude


def diffusefraction(radG, alt, Kt, Ta, RH):
    """
    This function e
    :param radG:
    :param altitude:
    :param Kt:
    :param Ta:
    :param RH:
    :return:

    """
    # lat = location['latitude']
    # lon = location['longitude']

    # altitude = altitude(lat,lon,datetime)

    alfa = alt * (np.pi / 180)

    if Ta <= -999.00 or RH <= -999.00 or np.isnan(Ta) or np.isnan(RH):
        if Kt <= 0.3:
            radD = radG * (1.020 - 0.248 * Kt)
        elif Kt > 0.3 and Kt < 0.78:
            radD = radG * (1.45 - 1.67 * Kt)
        else:
            radD = radG * 0.147
    else:
        RH = RH / 100
        if Kt <= 0.3:
            radD = radG * (1 - 0.232 * Kt + 0.0239 * np.sin(alfa) - 0.000682 * Ta + 0.0195 * RH)
        elif Kt > 0.3 and Kt < 0.78:
            radD = radG * (1.329 - 1.716 * Kt + 0.267 * np.sin(alfa) - 0.00357 * Ta + 0.106 * RH)
        else:
            radD = radG * (0.426 * Kt - 0.256 * np.sin(alfa) + 0.00349 * Ta + 0.0734 * RH)

    radI = (radG - radD) / (np.sin(alfa))

    # Corrections for low sun altitudes (20130307)
    if radD < 0:  # new addtion for Phoenix case
        radD = 0
    if radI < 0:
        radI = 0
    if alt < 10 and radI > radG:  # originally if alt<1
        radI = radG
    if radD > radG:
        radD = radG

    return radI, radD